1. Field of the Invention
The present invention relates to an apparatus as well as a process for recovering solvents, in particular, for manufacturing apparatuses of web-like materials, preferably sound tapes and video tapes.
In modern manufacturing plants there frequently is a need of purifying solvent-contaminated gases with inert gases, in particular, with liquid nitrogen. The transition into the liquid phase of the solvent to be condensed out is usually above the vaporization curve of liquid nitrogen. This may involve substantial functional difficulties, in particular, in the control of the outlet temperature of the carrier gas.
2. Description of the Prior Art
From German Patent Specification 1 032 218 there are known a method and an apparatus for the fractionated condensation of chemical vapor mixtures, which are treated in condensation vessels connected stage by stage with each other. In each condensation stage an intermediate medium is used between the actual cooling medium, that is air, and the vapor mixture to be fractionated. All of the chemical vapor mixtures mentioned there can be fractionated at relatively high temperatures. The possibly present residual gas, e.g. air or an inert gas, which has to be purified, contains a high amount of residues of the chemical vapor mixture to be fractionated.
From German Offenlegungsschrift 1 419 190 there are likewise known a method as well as an apparatus for condensing chemical vapor mixtures. There, too, chemical vapor mixtures boiling at relatively high temperatures are condensed by means of air cooling and an intermediate medium in such a way that, for one thing, the condensate does not freeze out, but, for the other, condensation is as substantial as possible. This published patent application predominantly deals with the control of the pertinent parameters.
From European Patent Specification 0 124 997 corresponding to U.S. patent application Ser. No. 481,177 there is known a method of recovering solvent vapor using an inert gas circuit for baking solvents out of a product within an oven, for one thing, and a cryogenic apparatus supplying transfer chambers belonging to the oven, for the other. Here, the inert gas circulation is a closed circuit, supplying the oven, after the inert gas, in general nitrogen, has been liberated from all solvents as required by safety regulations. The gaseous nitrogen which is produced by the purification of the inert gas is used for the supply of the transfer chambers which are adapted in such a way that no gas exchange takes place between the inert gas circuit and the oven.
In the method according to European Patent Specification 0 124 997 a relatively high amount of energy is necessary to recover the solvents and to maintain in the oven the temperature necessary for curing the products and/or for vaporizing the solvents from the products.